fan clutch?

[Daves72'GMC]

Are fan clutches the same for a big block versus small block trucks and how can I tell if mine is bad?

[tecky11]

dont know the dirrernce between the clutches, but if it is bad the fan will still spin even after motor is off

[Stocker]

When you rotate the fan by hand, there should be some resistance -- it should feel like it's mired in molasses.

Typically on startup, the fan will be engaged for a few seconds, maybe for several seconds, and you will hear the roar of it moving lots of air -- then it should 'release' and the roar goes away. Some of the more aggressive fans can be heard engaging/disengaging as you drive, depending on cooling needs of the engine.

If it never releases, or never engages, it's bad. Oh, check for a wobbly shaft too.

Some clutches are a two-piece 'clamshell' design that can be unbolted -- mine is one of those. The temperature-sensitive silicon fluid inside can go bad or become depleted, but it can be replaced. The only source I know of is from Toyota dealers -- it comes in a pricey little vial.

Mine went bad many years ago and I cleaned it out and put in fresh fluid -- it's been working perfectly ever since.

[Eichorst69]

The fan should stop turning when the engine stops. If the fan continues to spin then the fan clutch is bad.
And I believe the small block and big block clutces are different.

Rob

[Jim_PA]

I bought a heavy duty clutch from Advance, as soon as I start driving, it stays engaged for 10-15 seconds. I've been thinking of downgrading to a non-heavy duty clutch to see if it doesn't make as much noise, but I'm not convinced it's worth messing with.

[rwolf9653]

The part numbers on NAPA's website show different fan clutches. Probably just heavy duty vs. light duty